Mobile communication system standardization group, 3GPP (The 3rd Generation Partnership Project) is investigating EPS (Evolved Packet System) as a next generation mobile telecommunication system, and studying HeNB (Home eNodeB) as a small base station installed in a residence or the like as an EPS configurational apparatus (which will be referred to hereinbelow as home base station).
The home base station forms a small-scale wireless cell called a femtocell, which accommodates UEs (User Equipment: mobile terminal devices) using the same wireless access technique as that of a normal base station and establishes connection to the core network of the mobile communication system via a broadband line to be able to relay communication data of UEs accommodated therein.
Since the home base station uses the broadband line as backhaul and can be set by a general user, it is possible to easily extend the coverage area of the mobile communication system, especially the indoor coverage area. Further, since the radius of the cell is small and the cell can be exclusively used by a few users, it is possible to expect improvement in communication speed and frequency usage efficiency compared to an outdoor macro cell base station which a large number of users have to share.
Further, in non-patent document 2, local IP access function is defined as a functional requirement of a home base station. The local IP access is to provide for UEs connectivity to the network such as a network inside the home (which will be referred to hereinbelow as “home network”) to which the home base station is connected directly. For example, this enables a UE to connect another information terminal (printer etc.) that is connected to the home network (this will be called hereinbelow “home network connection service”), and also enables the UE to connect to the internet without passage of the core network of the mobile communication system (this will be called hereinbelow “internet connection service”).
Conventionally, if a UE performs direct communication with an appliance having no cellular communication interface such as a printer or the like, the UE needs to have a local area-use communication interface such as a wireless LAN etc. However, use of local IP access enables even a UE that has a cellular communication interface only to perform communication with other communication terminals within the home network because the home base station functions as a gateway between different wireless access schemes.
Since use of local IP access also makes it possible to connect to the internet without passage of the core network of the mobile communication system, it is possible to distribute traffic load (offload), from the perspective of the mobile network operator.
Further, differing from a microcell base station, the home base station can give access right only to a particular UE based on the form of the usage, and three access modes called closed, open and hybrid are defined. Each home station is allotted with a group identifier called CSGID (Closed Subscriber Group Identification). In the closed mode, the home base station can designate UEs to be permitted to connect for every CSGID. In the open mode, the home base station can give the right of access to the home base station to all UEs. In the hybrid mode, which is a combination of the closed mode and open mode, communication of UEs that are given with access right in closed mode can be handled preferentially.
Further, concerning local IP access, it is defined as a requisite that whether or not the user is permitted to use this function should be determined based on the user's subscription information. It is also ruled as a functional requisite that a UE can use local IP access and connection to the core network simultaneously when the UE is connecting to the home base station.
Moreover, non-patent document 3 discloses architecture candidates for embodying a home base station.